Importing FBX triangulates
Blender has an ability inside edit mode to convert triangles to quads. Press ALT + J with everything selected, or by selecting everything, CTRL + F for Face Menu, then Tris to Quads.

Edit: Something that might take you the rest of the way there is the Quadriflow Remesh tool. Its available in Blender 2.81+. As with all things unknown, I'd test it on a safe duplicate.